This invention relates to an apparatus for manufacturing powdered silicon nitride using fluidized bed techniques.
In a conventional fluidized bed furnace apparatus for the production of powdered silicon nitride, starting materials are continuously fed into a furnace while reacted powder is continuously removed from the furnace when it overflows. Such a conventional continuous production type apparatus has such a defect that some unreacted powder is removed from the furnace together with the reacted powder.
As disclosed in Japanese Laying-Open No. 60-251108, a batch-operated furnace apparatus is proposed which has a reaction furnace, a discharge port placed at a bottom portion of the reaction furnace, a discharge pipe connected to the discharge port, and a rod-like valve arranged in the discharge pipe in such a way that the valve can slide upwardly on the interior of the discharge pipe so as to close the discharge port if desired. In this batch-type apparatus, some reacted powder easily enters into a clearance between the discharge pipe and the valve so that the vale cannot move smoothly. Also, the effective sectional area of the discharge pipe for removing the reacted powder is so small that all of the reacted powder cannot be quickly discharged or removed.